Study On The Optimization Of Bending-duct In Road Tunnel And Smoke Outlets' Layout In Fire

In many long highway tunnel ventilation system, it often needs to consider the use of bending-ducts with diversion vanes. Firstly, by means of numerical simulation methods, this paper systematically studied the local loss coefficients of 30°,60°,90°bending-ducts and the ducts with the diversion vane types of concentric circle, wing, 107°thin circular, 95°thin circular. Secondly, the feasibility of replacing diversion vane by adjusted different bending-duct angle is compared and researched. Finally, for the controversy comes out in recent years about the use of smoke exhaust channel in long highway tunnel, the smoke exhaust effect of different channels and the reasonable layout of smoke outlets' vertical spacing are respectively studied according to the effect of smoke exhaust rate and fire environment improvement in tunnel.The main conclusions of this paper are:(1) In order to reduce the air resistance, the angle-θof the bending-duct with concentric circle diversion vanes must be either less than 30°or between 60°and 90°when r / D is less than 0.7;(2) For 90°bending-duct, the diversion effect of 95°thin circular vane is the best for all the vane types mentioned in the specification;(3) For ventilation engineering design, it could substitute 80°bending-duct for 90°bending-duct with diversion vanes;(4) The exhaust effect of arc-shaped smoke exhaust channel is the best, and the vertical spacing should be no more than 10m.